The present invention relates to seat suspension methods for vehicle seats.
Numerous vehicle seat suspensions are known, including those having air bag or air spring suspensions for resiliently supporting a seat in a selected position. In such suspension systems, pressurized air is delivered to or exhausted from the air bag to adjust the elevation of the seat. The use of an air bag permits upward and downward vibrations of the seat. To counteract these vibrations, shock-absorbing cylinders have been used to dampen the seat vibrations.
In one known approach, as the elevation of the seat suspension is changed by inflating or deflating the air bag, the shock absorbing cylinder has a piston supporting rod which extends or retracts, depending upon the direction in which the seat elevation is changed. In this approach, the shock absorbing cylinder must be capable of extension and retraction throughout the entire range of seat elevation adjustment. In addition, these seat suspension systems are understood to use shock absorbing cylinders with pistons that apply a constant dampening force over the full stroke of the piston. If the dampening force were non-constant in such systems, problems would ensue. For example, in such systems a non-constant dampening force would mean that the ride provided by the seat would vary depending upon the seat elevation.
U.S. Pat. No. 3,951,373 illustrates one form of seat suspension utilizing a shock absorbing cylinder and an air bag or air spring. In this construction, the shock absorber is understood to have a stroke which is capable of extending and retracting throughout the full range of seat height adjustment. However, in this construction, a hand knob may be operated to adjust the throw of a shaft to thereby change the effective length of the shock absorber.
Although numerous seat suspension systems are known, a need nevertheless exists for an improved seat suspension method having new and non-obvious differences over known approaches.
In accordance with one embodiment, a method of suspending a seat above the floor of a vehicle comprises positioning the seat at a first elevation relative to the floor of the vehicle, allowing the seat to move in response to vibrations, and applying a dampening force which varies non-linearly over at least certain ranges of seat movement in response to vibration so as to dampen the vibrations.
In accordance with another aspect of an embodiment of a seat suspension method, and regardless of whether a non-linearly varying dampening force is applied, the dampening force may be relieved during at least a portion of the time the seat is being shifted from one elevation to another elevation and then reapplied. The dampening force which is reapplied may be of the same magnitude as the dampening force that was applied to the seat immediately prior to relieving the dampening force.
Movement of the seat in response to vibrations may be limited to movements between first and second extremes of motion which are less than the overall range through which the elevation of the seat may be adjusted. The method may include the step of biasing the seat to a home position between the first and second extremes of motion. The method may also include the step of automatically returning the seat toward the home position in the event the seat moves outside of the first and second extremes of motion while the dampening force is being applied, such as in response to variations in the load on the seat. As a specific example, when a seat occupant rises from the seat, the seat may travel upwardly beyond the uppermost of the first and second extremes of motion, with the seat automatically being returned toward the home position under these conditions. Conversely, if the occupant then reoccupies the seat and the seat travels in the opposite direction downwardly beyond the other of the first and second extremes of motion, the seat may again automatically be returned toward the home position under these conditions.
As a further aspect of an embodiment of the method, the seat may be latched to secure the seat at a desired elevation and unlatched when the seat is adjusted to a different elevation. When latched, the seat is supported so as to permit movement in response to vibrations. In addition, a dampening force is applied to the seat to dampen the motion of the seat in response to such vibrations. The dampening force may be relieved at least during a portion of the time, and most preferably during the entire time, that the seat is unlatched for movement from one elevation to another. The dampening force may be relieved and reapplied simultaneously with the respective unlatching and latching of the seat.
In general, the seat may move between first and second extremes of motion in response to vibrations. With the seat in a latched condition, in the event motion of the seat exceeds either of the first or second extremes, for example when an occupant of the seat leaves or returns to the seat, the elevation of the seat may be adjusted to return the seat toward a home position between the first and second extremes of motion.
Inflation and deflation of an air spring may be used, in accordance with an embodiment of the method, to raise and lower the seat during seat height adjustment.
The present invention is directed toward novel and non-obvious aspects and/or advantages of a seat suspension method, individually and collectively. Aspects of embodiments of the method are set forth above and are further supplemented and described in the drawings and description which follows.